the united states drew a clear red line and iran backed off. now, red lines could be drawn in different parts of iran's nuclear weapons program. but to be credible, a red line must be drawn first and foremost in one vital part of their program. on iran's efforts to enrich uranium. let me explain why. basically any bomb consists of explosive material and a mechanism to ignite it. the simplest example is gun powder in a fuse. that is, you light the fuse, and you set off the gun powder. in the case of iran's plans to build a nuclear weapon, the gun powder is enriched uranium. the fuse is a nuclear detonator. for iran amassing enough uranium is far more difficult than producing the nuclear fuse. for a country like iran it takes many, many years to enrich uranium for a bomb. that requires thousands of centrifuges spinning in tandem in very big industrial plants. those iranian plants are visible and they are still vulnerable. in contrast, iran could produce the nuclear detonator, the fuse in a lot less time. maybe under a year. maybe only a few month